1. Field of the Invention
The present invention relates to a coil bobbin for a current transformer, which is incorporated into a microwave oven, an air conditioner, an electromagnetic cooking device or the like so as to be used in an electric current detecting portion of a circuit in a machine.
2. Description of Related Art
Conventionally, as shown in FIG. 8, this kind of current transformer is, for example, configured so as to have a primary coil 20 for detecting electric current, a coil bobbin 21 into which the primary coil 20 is incorporated, a secondary coil 22 wound around a winding drum of the coil bobbin 21, pin terminals 23 to which lead wires of the secondary coil 22 are connected, and a core 24 incorporated into the coil bobbin 21 including the primary coil 20 and the secondary coil 22, or the like.
In this current transformer, the primary coil 20 is formed from a thick CP wire or a copper wire to be bent in substantially U-shape, and inserted into a through hole 25 of the coil bobbin 21 to be incorporated into the coil bobbin 21.
In this case, for example, adhesive is used for fixing the primary coil 20 to the coil bobbin 21.
Alternatively, an eyelet 26 is mounted on each a pair of legs 20a of the primary coil 20, protruding from the bottom surface of the coil bobbin 21.
Another alternative is molding the primary coil 20 at the same time as molding the coil bobbin 21.
Using adhesive for fixing the primary coil 20 to the coil bobbin 21 has such defects that it takes too long in working process and that work control is hard to carry out.
Using the eyelets 26 has such defects that it causes an increase in the number of components and therefore in cost, and that a step of incorporating them is required.
Molding the primary coil 20 at the same time as molding the coil bobbin 21 has also such a defect that the molded component is expensive.
The present invention is achieved in view of the above and has its object to provide a coil bobbin for a current transformer which requires no adhesive or eyelets, and enables easy fixing of the primary coil to the coil bobbin without an increase in cost.
The present invention attains the above-described object according to a configuration wherein:
a coil bobbin 1 is formed with a primary coil mounting portion 7 and a primary coil fixing portion 8 at an outer surface of one of flanges 4 so as to protrude outwardly;
through holes 9, 9xe2x80x2 are formed at both sides of the primary coil mounting portion 7 and the primary coil fixing portion 8 respectively, and a pair of legs 3a of a primary coil 3 for detecting electric current extend through the through holes 9, 9xe2x80x2;
the primary coil fixing portion 8 is formed with a window 12 into which a jig is inserted;
the window 12 is formed with concave fixing portions 12a,
each of the legs 3a of the primary coil 3 is inserted into the through hole 9 of the primary coil mounting portion 7, the window 12 and the through hole 9xe2x80x2 of primary coil fixing portion 8, respectively; and
each of the legs 3a positioned in the window 12 is bent by the jig toward each of the fixing portions 12a to be fixed thereto.
In this case, the fixing portions 12a are formed at both side surfaces of the window 12.
Alternatively, the window 12 is formed, at a center thereof, with a column 8a, which is formed, at both side surfaces thereof, with the fixing portions 12a. 
Alternatively, the window 12 is formed, at an inner surface thereof, with the fixing portions 12a. 
In addition, positioning members 10 for positioning the primary coil 3 are formed at a top surface of the primary coil mounting portion 7, and a wall 11 formed at each of both ends of the primary coil mounting portion 7.
Moreover, the jig 14 is formed with a protrusion 14b, 14c, 14d whereby each leg 3a mounted to the coil bobbin 1 and positioned in the window 12 is partly urged to be bent.
Furthermore, a top of the jig 14 is bent in substantially L-shape to be formed, at its bent portion 14a, with the protrusion 14b, 14c, 14d in substantially V-shape.